1. Field of the Invention
The present invention relates to a tire wheel bearing apparatus for use in an automobile.
2. Description of the Prior Art
FIG. 4 shows an embodiment of a tire wheel bearing apparatus used in an automobile and a structure in the case of being employed for a driven wheel. The bearing apparatus is structured such that a hub wheel 1 is rotatably supported by an axle bearing 2, a tire wheel is fixed to the hub wheel 1 and the axle bearing 2 is supported by a suspension apparatus of a vehicle body via a knuckle 3. The axle bearing 2 is a double-row ball-or roller bearing and is constituted by an outer wheel 6 in which double-rows of track surfaces 4 and 5 are formed on an inner diameter surface, inner wheels 9 and 10 in which track surfaces 7 and 8 are formed on an outer diameter surface, double-rows of rolling elements 11 interposed between the outer wheel 6 and the inner wheels 9 and 10, and a retainer 12 retaining the rolling elements 11 in the respective rows at equally spaced interval in a circumferential direction. The outer wheel 6 is force fitted to the knuckle 3 and fixed by a stop ring 13. In order to prevent foreign materials from entering into the axle bearing 2 and prevent a grease filled therewithin from leaking out, seals 14 and 15 are provided. In the illustrated example, a double-row angular ball bearing is employed as the axle bearing 2. The hub wheel 1 is provided with a flange 16, and hub bolts 17 for fixing the tire wheel is mounted to the flange 16 at equally spaced interval in a circumferential direction. Further, a brake rotor 18 is fixed to the flange 16 of the hub wheel 1 by the hub bolts 17. The inner wheels 9 and 10 of the axle bearing 2 are force fitted to an outer diameter of an end portion of the hub wheel 1, and a protruding end portion of the hub wheel 1 is fixed by a nut 19, whereby an assembly is performed.
In the conventional tire wheel bearing apparatus mentioned above, since the outer wheel 6 of the axle bearing 2 is force fitted to the knuckle 3 having the outer non-circular profile in a strong tight manner, there is a case that the track surfaces 4 and 5 of the outer wheel 6 are deformed. Due to the deformation mentioned above, an axial run out of the bearing or the like is deteriorated, and an axial run out (or a surface run out) is generated in the brake rotor 18 mounted to the flange 16 of the hub wheel 1 after force fitted to the knuckle 3, thereby causing a vibration at a time of braking after a high speed travel of the automobile and causing uneven wear of the brake. Further, it can be considered that a high preload is applied so as to increase a rigidity of the bearing, however, since there is a fitting portion between the hub wheel 1 and a pair of inner wheels 9 and 10 and between the outer wheel 6 and the knuckle 3, it is unavoidable that a dispersion range of a gap reduction amount due to the preload is increased in view that the fitting tolerances are accumulated, so that the structure can not always apply a sufficient preload.
Accordingly, an object of the present invention is to provide a tire wheel bearing apparatus which can restrict an axial run out of a brake rotor by improving a rigidity of a bearing.
According to an embodiment of the present invention, a tire wheel bearing apparatus comprises:
an outer member having double-rows of track surfaces integrally provided on an inner periphery;
an inner member having a tire wheel mounting flange provided at one end thereof, a cylindrical small diameter step portion provided at another end thereof and double-rows of track surfaces formed by force fitting the inner wheel to the small diameter step portion so as to oppose to the track surfaces of the outer member; and
double-rows of rolling elements interposed between both of the track surfaces in the outer member and the inner member;
the inner wheel force fitted being fixed to the inner member by caulking the end portion of the small diameter step portion of the inner member radially outwardly,
wherein each of the rolling elements is installed between the track surfaces in the outer member and the inner member with contact agnle, and a bearing clearance is set to be negative.
The present invention is applicable to a structure of the type in which the track surface in the tire wheel mounting flange side among the track surfaces of the inner member is directly formed on an outer periphery of the inner member, as well.
In accordance with the present invention, the following advantages can be obtained:
(1) It is possible to so design that a span of the bearing is set to be wide within the same space and it is possible to largely improve a rigidity of the bearing.
(2) It is possible to change specifications of the inner portion within the same space, increase the number of the rolling elements so as to improve the rigidity of the bearing and optimize a thickness of the outer member and a thickness of the flange so as to restrict a deformation of the outer member, thereby improving the rigidity of the bearing.
(3) It is possible to restrict a dispersion range of an amount of a preload after being assembled to a narrow range. The higher the preload is, the higher the rigidity of the bearing is. In the tire wheel bearing apparatus in accordance with the present invention, since the number of the fitting portion is reduced, a dispersion component of the gap reduction amount due to the fitting tolerance becomes zero, so that a low preload area generated due to the accumulation of the tolerance is eliminated.
In the tire wheel bearing apparatus in accordance with the present invention, the structure can be made such that the rolling element is a ball. Further, the structure can be made such that a vehicle body mounting flange is integrally formed on an outer periphery of the outer member, the inner member is formed in a hollow shape, and an uneven engaging structure for transmitting a torque, for example, any one selected among a serration, a spline and a key is integrally provided in the inner member.
The bearing rigidity can be easily improved, and the axial run out of the brake rotor can be restricted in the case of attaching the brake rotor to the tire wheel mounting flange of the inner member. Further, in the bearing structure, since the inner wheel force fitted is fixed to the inner member by caulking the end portion of the small diameter step portion of the inner member radially outwardly, it is possible to easily realize the light weight and the compact size of the whole of the apparatus.
Further, when the structure is made such that the inner member is formed in a hollow shape, or the uneven engagement portion for transmitting the torque, for example, any one selected among the serration, the spline and the key, is integrally provided in the inner member, the tire wheel bearing apparatus in accordance with the present invention can be commonly used for the drive wheel in addition to the structure for the driven wheel. In the drive wheel side, at a time of assembling the constant velocity joint, it is not necessary to adjust the bearing clearance due to the control of the fastening torque of the nut.
Another object of the present invention is to provide a tire wheel bearing apparatus which can more restrict uneven wear of a brake rotor and a brake judder by paying attention to the other reasons for generating a surface run out of the brake rotor then an improvement of accuracy in each of the parts themselves.
According to another embodiment of the present invention, a tire wheel bearing apparatus comprises:
an outer member having double-rows of track surfaces on an inner periphery;
an inner member having track surfaces opposing to the respective track surfaces;
a bearing constituted by double-rows of rolling elements interposed between the outer member and the inner member;
the inner member and a connected member being integrally by fastening means; and
a tire wheel mounting flange being provided in any one of the outer member, the inner member and the connected member,
wherein a preload is applied to the bearing and the inner member and the connected member are integrally connected by the fastening means with a predetermined axial force or more. In this case, for example, in the case of applying the present invention to the bearing apparatus of the front wheels of the Front Wheel drive vehicle, the connected member becomes an outer joint member of a constant velocity joint. Further, the present invention can be applied to a structure that the outer member is rotated in addition to the structure that the inner member is rotated.
In addition to the improvement of each of the parts themselves such as the run out of the mounting surface of the brake rotor itself, the flange run out of the hub wheel itself, the axial run out of the bearing, the assembling error (the misalignment) or the like, the rigidity of the bearing itself and the axial force between the inner member and the connected member can be improved, thereby further restrict the surface run out of the brake rotor and completely preventing the uneven wear of the brake rotor and the brake judder in an easy manner. Specifically, a rigidity of the bearing itself can be increased by applying the preload to the bearing, and a combining force (an axial force) between the inner member and the connected member can be increased by integrally connecting the inner member to the connected member by the fastening means with the predetermined axial force or more. Accordingly, in the case that the automobile is turned, since the predetermined axial force or more exists even when a load in a direction opposing to the axial force is generated due to a moment load or the like, the connection portion may not have an end play is not shaky, so that it is possible to restrict a surface run out of the brake rotor.
In the present invention, the preload is applied to the bearing, however, it is desirable to set an amount of the preload of the bearing to 981 to 9810 N (100 to 1000 kgf). When the amount of the preload is smaller than 981 N (100 kgf), it is hard to increase a rigidity of the bearing itself and the bearing clearance causes the surface run out of the brake rotor. On the contrary, when the amount of the preload is greater than 9810 N (1000 kgf), it is possible to increase the rigidity of the bearing itself, however, since the load of the bearing is increased at that degree, an excessive preload invites reduction of a service life of the bearing. Further, the axial force for integrally connecting the inner member to the connected member by the fastening means is preferably set to 9810 N (1000 kgf) or more.
Further, in accordance with the present invention, the structure is desirably made such that in the tire wheel bearing apparatus in which the brake rotor is mounted to the tire wheel mounting flange, a width of the run out of the brake rotor is restricted to a standard value in a state of being assembled in the automobile when rotating the brake rotor with reference to a fixed side member of any one of the outer member and the inner member. The tire wheel bearing apparatus with the brake rotor in which the width of the run out is previously restricted as mentioned above has a high reliability, and the problem of the surface run out of the brake rotor can be solved by using the apparatus as it is in the automobile assembling plant. In this case, it is desirable that the standard value of the axial run out of the brake rotor is set to 50 xcexcm or less.
Other object of the present invention is to provide a bearing apparatus for a drive wheel which can solve the problems in the prior art mentioned above, is compact and light and improves a durability.
In accordance with other embodiment of the present invention, a bearing apparatus for a drive wheel comprises:
a tire wheel bearing portion in which a rolling element is assembled between an outer member having a mounting flange for mounting to a vehicle body and an inner member having a tire wheel mounting flange for mounting a tire wheel so as to rotatably support the inner member;
a constant velocity joint portion provided at one end of a drive shaft and constituted by an outer joint member having a track groove formed on an inner periphery, an inner joint member having a track groove opposing to the track groove of the outer joint member formed on an outer periphery, and a ball assembled between the track groove of the outer joint member and the track groove of the inner joint member;
a rotation of the outer joint member in the constant velocity joint portion being transmitted to the inner member of the tire wheel bearing portion,
wherein a serration portion fitted to the inner member is formed in the outer joint member by hardening, the outer joint member has a caulked portion at an end portion, and the caulked portion is not hardened.
In accordance with the present invention, the non-hardened area having a low hardness is provided in the end portion of the outer peripheral surface of the inner fitting member among the inner member (the hub wheel) and the outer joint member fitted to each other, whereby there can be obtained a hardening pattern optimum for the bearing apparatus for the drive wheel of the type caulking the end portion so as to connect both of the members. That is, since the portion serving as the connecting means between the inner member and the outer joint member can be stably caulked by applying a service life resistance to the track surface on which the rolling elements roll, in particular, the inner track surface portion and on the contrary providing the non-hardened area in the end portion, it is possible to obtain the bearing apparatus for the drive wheel with no preload extraction and having a compact structure. Further, since the connection between the inner member and the outer joint member is not performed by welding, it is possible to solve the disadvantages that a thermal strain is generated on the track surface or the like. The torque transmission between both of the elements can be securely achieved by the serration portion.
The rolling element may be constituted by double-rows of rolling elements, double-rows of outer track surfaces are formed on the outer member, and one of double-rows of inner track surfaces opposing to the double-rows of outer track surfaces is arranged in the inner member and the other in the outer joint member. Here, since it is possible to employ a spline in place of the serration as is well known, the serration in this case means a serration or a spline. Further, the axial size is made 10% or more compact by forming the track surface (the inner track surface in the inboard side) in the outer joint member of the constant velocity joint. A turning radius of the automobile is restricted by the maximum operating angle of the fixed type constant velocity joint. Accordingly, in recent years, there is required a constant velocity joint which can set the operating angle to be greater for reducing the turning radius. The bearing apparatus for the drive wheel in accordance with the present invention is compact in the axial direction so as to coincide the center of operation of the fixed type constant velocity joint with the center of the king pin, thereby making the turning radius of the automobile small.
A continuous hardened layer may be formed between the another inner track surface portion and the serration portion among an outer surface of the outer joint member.
The outer joint member may be of a carbon steel containing 0.45 weight % or more carbon amount. By using the carbon steel containing 0.45 weight % or more, preferably 0.5 to 0.7 weight % carbon amount for the material constituting the outer joint member, it is possible to provide a portion in which a desired hardened layer is formed in accordance with a heat treatment and a portion having a ductility for being caulked, in the outer joint member. Further, by making the outer joint member of the carbon steel containing 0.45 weight % or more carbon amount, it is sufficiently secure a rolling fatigue service life (a flaking service life) of the another inner track surface (the inner track surface on the inboard side) formed in the outer joint member, in spite of a load repeatedly applied from the rolling elements. That is, in order to secure the rolling fatigue service life, it is necessary to set a hardness of the surface portion of the inner track surface in the inboard side to be high to a degree, for example, about Hv 550 to 900. When the hardness of the surface portion is low, the rolling fatigue service life of the inner track surface in the inboard side becomes short. In the case of forming the outer joint member by the carbon steel containing the carbon less than 0.45 weight %, a necessary hardness can not be obtained even if a hardening treatment is applied to the inner track surface on the inboard side. On the contrary, since the outer joint member is made of the carbon steel containing 0.45 weight % or more carbon amount and the inner track surface portion in the inboard side is hardened in accordance with a hardening treatment, it is possible to sufficiently increase the hardness of the inner track surface portion in the inboard side so as to secure a rolling fatigue service life of the inner track surface portion in the inboard side. Even in the case of securing the rolling fatigue service life of the inner track surface portion in the inboard side in the manner mentioned above, an axial end portion of the outer joint member is kept raw without being applied a hardening treatment. Accordingly, it is not troublesome to work the caulked portion for connecting the outer joint member and the hub wheel.
The outer joint member before being hardened may have hardness between Hv 200 and 300.
A hardened layer may be formed on an inner surface of the inner member. Since the hardened layer is formed on the inner surface of the inner member, it is possible to prevent the inner member from being deformed even when a great load is applied to the inner member together with the caulking process of the axial end portion of the outer joint member, thereby preventing a bearing clearance (positive or negative) from being shifted from a desired value. That is, in order to caulk and widen the axial end portion of the outer joint member so as to form the caulked portion, it is necessary to apply a great load directing outward in a diametrical direction to this axial end portion. As a result, a great surface pressure is applied to the inner peripheral surface and the end surface of the inner member together with a forming operation of the caulked portion. Accordingly, when the hardness of the inner member is low, the inner member is deformed due to the surface pressure mentioned above and the bearing clearance is shifted from the desired value. On the contrary, since the hardened layer is formed on the inner surface of the inner member, a hardness of the inner member is sufficiently high, so that it is possible to prevent the inner member from being deformed in spite of the great surface pressure, and it is possible to keep the bearing clearance in the desired value. Further, it is possible to prevent the diameter of the one inner track surface (the inner track surface on the outboard side) formed on the outer peripheral surface of the inner member from being changed and prevent an accuracy of shape (deviation from circular form and cross sectional shape) from being deteriorated, thereby preventing the rolling fatigue service life of the inner track surface on the outboard side from being reduced.
The constant velocity joint part may comprise an outer joint member in which eight curved track grooves extending in an axial direction are formed on a spherical inner peripheral surface, an inner joint member in which eight curved track grooves extending in an axial direction are formed on a spherical outer peripheral surface, torque transmitting balls assembled in each of eight ball tracks formed by pairs of the track grooves of the outer joint member and the track grooves of the inner joint member one by one, and a retainer for retaining the torque transmitting balls within the same plane. It is possible to achieve a light weight, a compact size, a low heat generation and a high efficiency in comparison with the constant velocity joint using six torque transmitting balls by employing the constant velocity joint using eight torque transmitting balls, and a light weight can be achieved by being integrally formed with the tire wheel bearing together with the compact size in the axial direction. It becomes very important in view of protecting an environment and saving an energy to reduce the weight of the whole of the automobile. In the parts used in the tire wheel portion such as the bearing apparatus for the drive wheel, it is possible to reduce an unsprung weight, thereby largely improving a steering stability of the automobile and applying a comfortable feeling. Further, a torque loss at a time of transmitting a rotational force is 30% improved, and the effect can be further improved particularly when a large operating angle is employed. Since the heat generation from the constant velocity joint at a time of driving can be about 20xc2x0 C. reduced in comparison with the comparative products, an influence with respect to the bearing service life can be reduced even when forming the track surface in the outer joint member of the constant velocity joint. Since the heat radiating performance of the constant velocity joint and the bearing portion is improved by employing the hollow structure, the resisting service life of the constant velocity joint and the bearing portion is largely improved and a reliability is increased.
The ratio (r1=PCDBALL/DBALL) between a pitch circle diameter (PCDBALL) of the torque transmitting ball and a diameter (DBALL) of the torque transmitting ball may be equal to or more than 3.3 and equal to or less than 5.0 (3.3xe2x89xa6r1xe2x89xa65.0). Here, the pitch circle diameter (PCDBALL) of the torque transmitting ball is twice a length of a line connecting between a center of the track groove of the outer joint member or a center of the track groove of the inner joint member and a center of the torque transmitting ball (PCDBALL=2xc3x97PCR). The length of the line connecting between the center of the track groove of the outer joint member and the center of the torque transmitting ball is equal to the length of the line connecting between the center of the track groove of the inner joint member and the center of the torque transmitting ball. Accordingly, a constant velocityity of the joint can be secured. Hereinafter, the size is referred to as xe2x80x9cPCRxe2x80x9d. The relation 3.3xe2x89xa6r1xe2x89xa65.0 is established because a strength of the outer joint member or the like and a load volume and a durability of the joint can be secured to be equal or more that of the structure using six torque transmitting balls. That is, in the constant velocity joint, it is hard to widely change the pitch circle diameter (PCDBALL) of the torque transmitting ball within a limited space range. Accordingly, a value r1 is mainly dependent upon the diameter (DBALL) of the torque transmitting ball. In the case that the ratio r1 is smaller than 3.3 (r1 less than 3.3) mainly corresponding to the case that the diameter DBALL is great, a thickness of the outer joint member, the inner joint member and the other parts is too thin to generate a risk in view of strength. On the contrary, in the case that the ratio r1 is over 5.0 (r1 greater than 5.0) mainly corresponding to the case that the diameter DBALL of the torque transmitting ball is small, the load volume becomes small, thereby generating a risk in view of durability. Further, since a contact oval of a contact portion becomes small when the diameter DBALL becomes small, a surface pressure of the contact portion between the torque transmitting ball and the track groove is increased, and there is a risk of causing a lack of a groove shoulder edge portion in the track groove or the like. By establishing the relation 3.3xe2x89xa6r1xe2x89xa65.0, it is possible to secure the strength of the outer joint member and the load volume and the durability of the constant velocity universal joint to be equal or more than those of the structure using six torque transmitting balls.
The ratio r2 (=DOUTER/PCDSERR) between an outer diameter (DOUTER) of the outer joint member and a pitch circle diameter (PCDSERR) of a tooth form formed in an axial hole of the inner joint member may be equal to or more than 2.5 and equal to or less than 3.5 (2.5xe2x89xa6r2xe2x89xa63.5). The relation 2.5xe2x89xa6r2xe2x89xa63.5 is established for the following reasons. That is, the pitch circle diameter (PCDSERR) of the tooth form of the inner joint member can not be largely changed in connection with a strength of an opposing shaft or the like. Accordingly, the value r2 is mainly dependent upon the outer diameter (DOUTER) of the outer joint member. In the case that the value r2 is smaller than 2.5 mainly corresponding to the case that the outer diameter DOUTER is small, a thickness of the outer joint member, the inner joint member and the other parts is too thin to generate a risk in view of a strength. On the contrary, in the case that the ratio r2 is over 3.5 mainly corresponding to the case that the outer DOUTER is great, there is a case that a problem on practical use is generated in view of a size or the like, and it is impossible to achieve a target for making compact. By establishing the relation 2.5xe2x89xa6r2xe2x89xa63.5, it is possible to secure the strength of the outer joint member and the like and the durability of the joint to be equal or more than those of the structure using six torque transmitting balls, and it is possible to satisfy a requirement on practical use. In particular, there is an advantage that the outer size can be made compact by establishing the relation 2.5xe2x89xa6r2 greater than 3.2. In this case, in the structure using six torque transmitting balls, the relation r2xe2x89xa73.2 is generally established.
A hollow cylindrical portion may be provided in at least an end portion of the shaft portion of the outer joint member.
The hollow cylindrical portion may extend through the shaft portion of the outer joint member so as to be communicated with a bottom of the mouth portion.
The bearing apparatus for a drive wheel may comprise:
a bearing portion in which a rolling element is assembled between an outer member having a mounting flange for mounting to a vehicle body and a hub wheel having a tire wheel mounting flange for mounting a tire wheel so as to rotatably support the hub wheel;
a constant velocity joint portion provided at one end of a drive shaft and constituted by an outer joint member having a track groove formed on an inner periphery, an inner joint member having a track groove opposing to the track groove of the outer joint member formed on an outer periphery, and a ball assembled between the track groove of the outer joint member and the track groove of the inner joint member;
the outer joint member of the constant velocity joint portion and the hub wheel of the bearing portion being fitted to each other so as to transmit a rotation of the outer joint member to the hub wheel,
wherein the fitting portion is formed by an inserting portion and a serration portion, and an end portion of an inner fitting member among the outer joint member and the hub wheel fitted to each other is caulked so as to fix both elements.
The inserting portion may be shorter than a length of the serration portion. By setting a relation between a length LF of the inserting portion and a length LS of the serration portion to LS greater than LF, the serration portion at first starts engaging at a time of assembling the outer joint member in the hub wheel, and an inserting operation is started after a phase in a peripheral direction is aligned, so that a force fitting operation can be easily performed.
The length of the inserting portion may be one fourth or more of a diameter of the inserting portion. Since a radial load of the bearing is applied to the inserting portion, the surface pressure becomes high in the case that the length of the inserting portion is less than one fourth of the axial diameter of the inserting portion, thereby causing a problem.
A fastening margin of the inserting portion may be equal to or more than 0 and equal to or less than 60 xcexcm. A lower limit of the fastening margin of the inserting portion is set to 0 xcexcmxe2x89xa6S in view of the bearing retaining rigidity, and an upper limit thereof is set to Sxe2x89xa660 xcexcm so that a force fitting force obtained by combining the serration portion and the inserting portion becomes equal to or less than an axial force of the nut.
A still other object of the present invention is to achieve a practical use of a kind of bearing apparatus for a drive wheel by securely and easily controlling a negative clearance of a bearing in a bearing apparatus of a drive wheel structured such as to form one inner track surface among double-rows of inner track surfaces on an outer periphery of an axle and form another inner track surface on an outer periphery of an outer joint member in a constant velocity joint.
The present invention has the following effects.
(1) Since in the manufacturing (assembling) step of the bearing, the force fitting of the axle to the outer joint member is temporarily stopped in a state that the bearing axial clearance is positive, the axial moving amount of the outer wheel is measured in this state, and the axle is further force fitted at an amount over the measured value, whereby the force fitting is completed, it is possible to accurately and easily measure the bearing negative clearance of the bearing apparatus of the tire wheel obtained by integrally assembling the tire wheel bearing and the constant velocity joint so as to unit. Further, it is possible to apply to the bearing apparatus for the drive wheel using no nut, thereby being excellent in a wide use.
(2) It is possible to obtain a significantly high reliability in view of a bearing service life, a rigidity and a fretting of the bearing apparatus of the tire wheel in which the tire wheel bearing and the constant velocity joint are integrally assembled so as to be united.
(3) By bringing the shoulder portion of the outer joint member into contact with the end surface of the axle so as to complete the force fitting, a positional shift due to a fine movement of the outer joint member can be avoided and a stable bearing negative clearance can be maintained, whereby a reliability can be improved.
In accordance with a still other embodiment of the present invention, a bearing apparatus for a drive wheel comprises:
a tire wheel bearing portion having an outer member provided with a mounting flange for mounting to a vehicle body on an outer periphery and double-rows of track surfaces on an inner periphery, and an inner member arranged in an inner side of the outer member via a rolling element and provided with a tire wheel mounting flange for mounting a tire wheel and track surfaces on an outer periphery;
a constant velocity joint portion provided at one end of a drive shaft and including an outer joint member having a track groove formed on an inner side, an inner joint member having a track groove corresponding to the track groove of the outer joint member formed, and a ball arranged between both track grooves of the outer joint member and the inner joint member;
one row of the track surfaces of the tire wheel bearing portion being provided on an outer diameter surface of the outer joint member so as to integrally form the tire wheel bearing portion and the constant velocity joint member,
wherein a bearing clearance of the tire wheel bearing portion is a negative clearance controlled on the basis of a measured value in a state that the inner member is brought into contact with the shoulder portion of the outer joint member.
Alternatively, a bearing apparatus for a drive wheel may comprises:
a tire wheel bearing portion having an outer member provided with a mounting flange for mounting to a vehicle body on an outer periphery and double-rows of track surfaces on an inner periphery, and an inner member arranged in an inner side of the outer member via a rolling element and provided with a tire wheel mounting flange for mounting a tire wheel and track surfaces on an outer periphery;
a constant velocity joint portion provided at one end of a drive shaft and including an outer joint member having a track groove formed on an inner side, an inner joint member having a track groove corresponding to the track groove of the outer joint member formed, and a ball arranged between both track grooves of the outer joint member and the inner joint member;
one row of the track surfaces of the tire wheel bearing portion being provided on an outer diameter surface of the outer joint member so as to integrally form the tire wheel bearing portion and the constant velocity joint member,
wherein a bearing clearance of the tire wheel bearing portion is a negative clearance controlled on the basis of a measured value in a state that the inner member is connected to the outer joint member.
The track surface may be directly formed on an outer diameter surface of the outer joint member.
The bearing clearance may be controlled by temporarily stopping the force fitting in a state that the bearing axial clearance is positive at a time of integrally forming the outer joint member and the inner member by the force fitting, calculating a clearance (S) between the shoulder portion of the outer joint member and the end surface of the opposing inner member in this state, measuring a bearing axial clearance (xcex94axe2x80x2) in this state and thereafter force fitting until the end surface of the inner member is brought into contact with the shoulder portion of the outer joint member, thereby determining a negative bearing axial clearance (xcex94a) from a formula xcex94a=xcex94axe2x80x2xe2x88x92S.
In accordance with an aspect of the present invention, a method of producing a bearing apparatus for a drive wheel may comprise the steps of temporarily stopping a force fitting in a state that the bearing axial clearance is positive at a time of integrally forming the outer joint member and the inner member by the force fitting, calculating a clearance (S) between the shoulder portion of the outer joint member and the end surface of the opposing inner member in this state, measuring a bearing axial clearance (xcex94axe2x80x2) in this state and thereafter force fitting until the end surface of the inner member is brought into contact with the shoulder portion of the outer joint member, thereby determining a negative bearing axial gap (xcex94a) from a formula xcex94a=xcex94axe2x80x2xe2x88x92S.
In this case, when the force fitting is temporarily stopped before the end surface of the inner member is brought into contact with the shoulder portion of the outer joint member at a time of force fitting the axle to the outer joint member of the constant velocity joint, the bearing axial clearance is in a positive state, and the axial clearance xcex94axe2x80x2 actually exists. Accordingly, the negative bearing axial clearance xcex94a at a time of completion of the force fitting at which the shoulder portion of the outer joint member is brought into contact with the end surface of the inner member can be securely measured by measuring the interval S between the shoulder portion of the outer joint member at a time of temporarily stopping the force fitting and the end surface of the opposing inner member, and the bearing axial clearance xcex94axe2x80x2 corresponding to an axial amount of movement of the outer member at this time, and subtracting the interval S from the bearing axial clearance xcex94axe2x80x2. The interval S can be measured as by providing an air passage communicating with the interval S in the axle or the like, injecting a compressed air into the interval S from the air passage and detecting a back pressure, a flow amount, a flow speed and the like of the compressed air at this time. Further, the gap S can be also accurately determined by measuring an amount of force fitting stroke of the inner member at a time of moving after temporarily stopping the force fitting of the inner member force fitted to the outer joint member before completing the force fitting.
As mentioned above, since the negative bearing axial clearance xcex94a at a time of completing the force fitting at which the end surface of the inner member is brought into contact with the shoulder portion of the outer joint member can be securely measured, it is possible to accurately and easily measure the negative bearing clearance of the bearing apparatus of the tire wheel in which the tire wheel bearing and the constant velocity joint are integrally assembled so as to form a unit, and it is possible to connect the inner member force fitted to the outer joint member in accordance with a caulking method or the like without using a nut. Further, it is not necessary to provide an interval between the inner member and the outer joint member at a time of completing the force fitting, and a fine movement in an axial direction of both of the elements is lost by making the interval zero, whereby a reliability can be improved. Further, since the bearing negative clearance can be securely secured, it is possible to increase a range of an initial gap of the bearing, whereby it is possible to reduce a rate of inferiority.
Still a further object of the present invention is to control a clearance by actually measuring a bearing axial clearance having a direct relative relation with an amount of a preload in place of indirectly understanding the amount of the preload on the basis of a torque or the like, in order to provide a bearing apparatus of a tire wheel in which a proper preload amount is secured.
The present invention provides a bearing apparatus of a tire wheel in which a proper preload amount is secured by controlling a negative bearing axial clearance on the basis of a value actually measured in a step of assembling the bearing apparatus of the tire wheel. A basic idea of the clearance control in accordance with the present invention is as follows. At first, in a step of assembling the bearing apparatus of the tire wheel, a force fitting is temporarily stopped in the middle of the step of force fitting an inner member (an axle and an inner track wheel or the axle and an outer joint member) and a bearing axial clearance xcex40 and an assembly width T0 between the axle and the inner track wheel or the outer joint member. Next, the force fitting is continuously performed, an assembly width T1 is measured in a state of completing the force fitting, and a bearing axial clearance xcex41=xcex40xe2x88x92(T0xe2x88x92T1) is determined. Next, a caulking operation is performed, and an assembly width T2 after caulking is measured. Since the bearing axial clearance is reduced due to the caulking operation, the amount of the preload is increased, however, a gap reduction amount (preload increase amount) can be expressed by the formula T1xe2x88x92T2. The bearing axial clearance (preload amount) xcex42 in a final assembled product in which the caulking operation is completed can be determined in accordance with the formula xcex42=xcex41+(T1xe2x88x92T2). Since the preload is controlled by actually measuring the assembly widths T0, T1 and T2 and the initial bearing axial gap xcex40 in the step of assembling the bearing apparatus of the tire wheel, it is possible to control and secure a proper preload amount with respect to all the products, and a reliability of the product can be widely improved. Accordingly, since the bearing apparatus of the tire wheel in accordance with the present invention can directly measure the amount of the preload (the bearing axial gap) in place of converting the torque so as to indirectly understanding the amount of the preload in the structure in accordance with the conventional art mentioned above, it is possible to 100% control the amount of the preload of all of the products within the process so as to secure a shipping quality, whereby a high reliability can be provided. In this case, since the inner track wheel is deformed not only in an axial direction but also in a radial direction so as to give an influence to the bearing axial gap when fixing the inner track wheel by the caulking operation, a more accurate clearance control can be achieved by previously measuring a deforming amount of the inner track wheel mentioned above and converting the value into an axial direction so as to add the value to the actually measured value of the bearing axial clearance.
In accordance with a still further embodiment of the present invention, a bearing apparatus of a tire wheel comprises:
an outer member having a first flange for mounting to a vehicle body on an outer periphery and double-rows of outer wheel tracks on an inner periphery;
an inner member having a second flange for mounting a tire wheel on an outer periphery and double-rows of inner wheel tracks on an outer periphery;
double-rows of rolling elements interposed between the outer wheel tracks and the inner wheel tracks;
the inner member being constituted by an axle having the second flange and an inner track wheel fixed by force fitting to the axle and caulking an end portion of the axle; and
the double-rows of inner wheel tracks being arranged in the axle and the inner track wheel in a distributing manner,
wherein a bearing clearance is actually measured and controlled to be negative.
One of the double-rows of inner wheel tracks may be directly formed on the outer peripheral surface of the axle.
In accordance with an aspect of the present invention, a method of controlling a bearing clearance in the bearing apparatus of the tire wheel comprises:
an outer member having a first flange for mounting to a vehicle body on an outer periphery and double-rows of outer wheel tracks on an inner periphery;
an inner member having a second flange for mounting a tire wheel on an outer periphery and double-rows of inner wheel tracks on an outer periphery;
double-rows of rolling elements interposed between the outer wheel tracks and the inner wheel tracks;
the inner member being constituted by an axle having the second flange and an inner wheel fixed by force fitting to the axle and caulking an end portion of the axle; and
the double-rows of inner wheel tracks being arranged in the axle and the inner track wheel in a distributing manner,
wherein the method comprises the steps of:
temporarily stopping a force fitting in a state that the bearing axial gap is positive at a time of force fitting the inner track wheel into the axle, measuring an axial size T0 between a reference surface of the axle in this state and a reference surface of the inner track wheel and an initial bearing axial gap xcex40, and continuously force fitting the inner track wheel; and
measuring an axial size T1 between the reference surface of the axle and the reference surface of the inner track wheel after completing the force fitting of the inner track wheel, determining a bearing axial gap xcex41 after completing the force fitting on the basis of the formula xcex41=xcex40xe2x88x92(T0xe2x88x92T1), fixing the inner track wheel by caulking an end portion of the axle, measuring an axial size T2 between the reference surface of the axle and the reference surface of the inner track wheel after caulking, and determining a bearing axial gap after caulking xcex42 on the basis of the formula xcex42=xcex41+(T1xe2x88x92T2).
The bearing apparatus of a tire wheel may comprise:
an outer member having a first flange for mounting to a vehicle body on an outer periphery and double-rows of outer wheel tracks on an inner periphery;
an inner member having a second flange for mounting a tire wheel on an outer periphery and double-rows of inner wheel tracks on an outer periphery;
double-rows of rolling elements interposed between the outer wheel tracks and the inner wheel tracks;
the inner member being constituted by an axle having the second flange and an outer joint member of a constant velocity joint fitting to the axle and fixed in accordance with a caulking operation; and
the double-rows of inner wheel tracks being arranged in the axle and the outer joint member in a distributing manner,
wherein a bearing clearance is actually measured and controlled to be negative.
One of the double-rows of inner wheel tracks may be directly formed on the outer joint member.
One of the double-rows of inner wheels may be formed on an independent inner track wheel fitted to the outer joint member.
In accordance with an aspect of the present invention, there is provided a method of controlling a bearing clearance in the bearing apparatus of the tire wheel as previously recited comprising:
an outer member having a first flange for mounting to a vehicle body on an outer periphery and double-rows of outer wheel tracks on an inner periphery;
an inner member having a second flange for mounting a tire wheel on an outer periphery and double-rows of inner wheel tracks on an outer periphery;
double-rows of rolling elements interposed between the outer wheel tracks and the inner wheel tracks;
the inner member being constituted by an axle having the second flange and an outer joint member of a constant velocity joint fitting to the axle and fixed in accordance with a caulking operation; and
the double-rows of inner wheel tracks being arranged in the axle and the outer joint member in a distributing manner,
wherein the method comprises the steps of:
temporarily stopping a force fitting in a state that the bearing axial gap is positive at a time of force fitting the inner member into the outer joint member, measuring an axial size T0 between a reference surface of the axle and a reference surface of the outer joint member and a bearing axial gap xcex40, and continuously force fitting; and
measuring an axial size T1 between the reference surface of the axle and the reference surface of the outer joint member after completing the force fitting, determining an axial gap xcex41 after completing the force fitting on the basis of the formula xcex41=xcex40xe2x88x92(T0xe2x88x92T1), fixing the member to the outer joint member by the caulking operation, measuring an axial size T2 between the reference surface of the axle and the reference surface of the outer joint member after caulking, and determining an axial gap after caulking xcex42 on the basis of the formula xcex42=xcex41+(T1xe2x88x92T2).
The reference surface of the axle may be set to a flange surface of the second flange as in the invention stated in an eighth aspect, and may be set to an end surface of the second flange side as in the invention stated in a ninth aspect.